Restaurant digital orders have grown an average of 23 percent, per year since 2013, and will triple by the end of 2020, according to a report from NPD Group.

The report, called Delivering Digital Convenience, found that 70 percent of a restaurant’s digital orders come through its mobile app or its website, with the remaining orders coming through third-party apps or websites. Customers used the restaurant’s own app most of the time because of rewards points or savings, and other brands appeal to customers because they want to create a custom order or take friction out of the ordering process.

Third-party apps like DoorDash, UberEats or Grubhub/Seamless accounted for 40 percent share of the 20 most used apps, and are used by consumers who want to look up various food items and check prices.

“Digital orders will remain an outsized source of growth for the restaurant industry over the next few years, and operators who desire to grow need to embrace a digital strategy,” said David Portalatin, NPD food industry adviser and author of Eating Patterns in America, said in the announcement. “There are clear leaders in the digital ordering space, and third-party providers who have achieved critical mass the fastest.”